Death penalty is very difficult issue, from political side, medical, social, philosophical, religious etc.
In case of war, to defend the nation and people, soldiers can shoot and kill the enemy.
However, what if we are not at war?
Does society have a moral right to apply the principle of an eye for an eye, tooth for tooth, life for life, as in the Old Testament?
In the most countries in the world today, answer is simple no.
They do not want to destroy human life, but to rehabilitate the person and allow repentance and new life.
I think that such way is much more humanistic than death penalty practice today in America.
If someone is too dangerous for society, it is clear that we will not let him out.